Why did the FBI switch back to 9mm

A Brief History Of .40 S&W In Law Enforcement

The Miami Shootout of 1986 was the impetus for the Bureau's adoption of the .40 S&W cartridge. During the exchange of gunfire between FBI agents and two bank robbers, one of the criminals continued firing back despite being struck with multiple rounds of 9mm - ultimately killing two agents and wounding five others before succumbing to his injuries.

As the largest law enforcement entity in the United States, the FBI was able to conduct extensive ballistics research to identify the round with the best stopping power to immediately incapacitate armed suspects and avoid any more unnecessary loss of life. Preliminary studies demonstrated that 10mm was the optimal caliber, but it was ultimately deemed too heavy and difficult to control for the average agent to carry on duty.

This decision resulted in the collaboration between the Bureau and ammunition manufacturers to develop a stepped down, lighter recoiling handgun cartridge that would bridge the gap between 9mm and 10mm. The .40 S&W round provided the best of both worlds and quickly became the preferred ammunition of the FBI, with other agencies following suit.

Why Did The FBI Switch Back To 9mm?

The choice to transition back to 9mm was a practical one; tests indicated that modern 9mm defensive rounds (specifically, Speer Gold Dot G2) were delivering impressive terminal ballistics surpassing that of the .40 S&W. Handguns chambered in 9mm offered increased capacity and shootability without compromising stopping power, so were better suited for duty use.

Consequently, the FBI (and other law enforcment agencies) will continue carrying 9mm until the next new and improved pistol caliber is developed that outperforms modern defensive 9mm rounds.

Speer 24226 Gold Dot G2 9mm 147 GD2 - 20rd Box
Speer 24226 Gold Dot G2 9mm 147 GD2 - 20rd Box
$29 11
(1.456 per round)

9mm Is Back On Top... For Now

Provided you select a defensive load from a reputable manufacturer, 9mm is the best option for duty and EDC. It offers the greatest versatility and is the most practical choice out of anything that is currently available in today's market.

Hornady 90236 Critical Duty 9mm Luger 135 GR FlexLock - 25rd Box
Hornady 90236 Critical Duty 9mm Luger 135 GR FlexLock - 25rd Box
$29 54
(1.182 per round)

Be sure to watch our video to learn more about the history of the .40 S&W cartridge and why it fell out of favor with the FBI, plus hear Clint and Kaya's thoughts on modern 9mm ammunition!

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